The evil thing is a change from 3e. There are many roles for a ranger specialized against his own kind that don't involve being a vicious, predatory killer. Finding lost children. Hunting criminals. High elves vs Drow or half-orcs defending against orc raiders.

Indeed, I rule that your not evil for having favored enemy (your own species) because favored enemy may be just part of you specializing hunting down criminals, scumbags, thugs, bandits or know overall human behavior and anatomy so well you fight better against them.